#!/usr/bin/perl

use warnings;
use strict;

my $text1 = 'aapnootmies';
my $text2 = 'aapnogeenaap';

my $text3 = $text1 . reverse($text2);

$text3 =~ s/(.*)(.*)(??{reverse $1})/$2/;

print("Without common start [$text3]\n");